The reduction of a gaseous transition metal halide such as silicon with an alkali metal such as sodium has been described in the prior art. In that procedure, a sweep of the reactor with dry argon has been utilized to exclude atmospheric moisture and oxygen before initiating the reaction. This is done to prevent the alkali metal from reacting with water and forming undesirable by-products. In an alternative procedure, a vacuum pump has been used to evacuate the reactor before introduction of the reactants in order to remove atmospheric moisture and oxygen. The use of dry argon results in the discharge into the ambient atmosphere of argon which is not recycled. The use of a vacuum chamber requires the use of a high strength reactor and sealing means that prevent the entry of atmospheric moisture and oxygen. The expense of constructing specialized vacuum reactors and the introduction of contaminants from seal lubricants or gaskets have rendered these approaches unsatisfactory. The applicants have discovered a process for removal of the ambient air and moisture from a reactor which avoids the need to use argon or a high vacuum. The process comprises the use of a non-reactive, condensible gas that is passed into the reactor to expel ambient air. Thereafter the reactor is filled with the gaseous transition metal halide and the non-reactive condensible gas is transferred to a condensing zone where it is separated from the gaseous transition metal halide. Thereafter the separated gaseous transition metal halide is recycled to the reactor and the non-reactive, condensed gas is placed in a reservoir from which it is recycled via an expansion valve when it is required to expel atmospheric moisture and oxygen from the reactor.